In the field of gymnastic machines the production of cardiovascular training equipment is well known, that allows simulating the execution of a physical activity, such as running or walking, by means of a cyclical load group, as well as of equipment designed to exchange power with the user through footrests forced to move along a given trajectory. Without limiting the general scope of the present invention, some gymnastic machines are well known, wherein the load group can be actuated through footrests, which can move along substantially elliptical trajectories and on which the user's feet constantly rest, allowing running or walking simulation avoiding injuries to the lower limb articulations. In view of what described above, these machines are usually called of the “elliptical type” or simply “elliptical”; they are provided with a load group usually comprising a wheel, to which two arms are connected through respective end portions in diametrically opposite position. Usually, a flywheel is mechanically coupled to this wheel for energy store to increase the footrest motion fluency. Each arm is furthermore connected, through a respective free end, to a longitudinal track, arranged laterally and parallel to the flywheel.
In view of the above description it is clearly apparent that each flywheel-arm pair is similar in structure to that described above, so as to operate according to the scheme of the rod-crank mechanism, also known as “crank and slider mechanism”, wherein the flywheel functions as a crank and each arm functions as a connecting rod and wherein the substantially horizontal track functions as the cylinder/tube of the mechanism. Each arm carries the corresponding footrest in intermediate position; a power dissipator is associated with the flywheel allowing to adjust the effort the user must exert on the pedals to perform the training exercise. It is therefore useful to specify that the object of the flywheel is to regulate the machine operation, making it fluent. In view of the above description, hereinafter reference will be usefully made to the terminology known to those skilled in the field of the crank and slider mechanisms, and therefore to the terms “top dead centre” and “bottom dead centre”, or, better, to their convenient forms “front dead centre” and “rear dead centre”, as in this case the axis of movement of the rod/arm ends is substantially horizontally arranged. The broad use of these terms will allow to talk about front dead centre and rear dead centre of arms/rods in, and of, the footrests based upon the context, even if only one of the speed components of these footrests will be null as the motion will be inverted.
In elliptical machines the track inclination can be fixed or variable, as it is well known from numerous examples of machines produced by the US firm Precor and from numerous US patents invented by Larry Miller, starting from the first U.S. Pat. No. 5,755,642 disclosing the operating principle of the elliptical machines, and the teachings of Robert E. Rodgers. In some versions of these machines, the load group comprises a flywheel arranged at the front, to facilitate the access to the machine; in other cases, and usually in the machines produced by Precor and embodying the patent US '642 and the following patents, the load group is arranged at the back. This complicates the access to the machine, that must necessarily occur from the side, as well as the descent from the footrests once the exercise has ended; in fact, the user must go down in the same way he/she has gone up, i.e. from the side and not backwards, as it would be spontaneous, to avoid tripping over the cover of the load group or the joint between the levers and the flywheel.
To overcome the prior art patents and the drawbacks illustrated above, many gymnastic machines for elliptical training are based upon mechanisms arranged at the front. On the other hand, drawbacks are associated with the front arrangement of the mechanism regulating the machine operation and the footrest movement along elliptical trajectories. It is useful to highlight one of these drawbacks, which can make the use of the machine particularly unpleasant. With reference again to the above illustrated analogy with the crank and slider mechanism, it should be noted that the front arrangement of the cranks/flywheel gives each footrest an acceleration peak when the corresponding connecting rod is at the rear dead centre. The greater the power exchanged by the user with the machine the more unpleasant is the perception of this acceleration peak; and the faster is the footrest actuation speed the more sharp is this perception, so that the effect is jargonally called “foot kick”. In view of the above description the elliptical gymnastic machines are poorly indicated for training sessions wherein high forces must be exchanged through the footrests, and they are therefore usually reserved for poorly conditioned users interested in performing low impact training.
In view of the above description, the problem of producing elliptical machines for practical and pleasant use as regards going up and down the footrests is currently unsolved, and represents an interesting challenge for the Applicant.
In view of the situation described above, as well as of a market growth of the cyclical machines that allow to perform cardio-vascular training by preventing articulation injuries, it would be desirable to have available a gymnastic machine provided with a device that, in addition to limit and possibly to overcome the typical drawbacks of the prior art illustrated above, defines a new standard of this type of equipment.